Here is one method for achieving the delightful harmony of Yin-Yang.
When the woman is laid on her back, the man enters between her raised knees, kissing her mouth and fondling her tongue with his. With his Jade Stalk, his penis, he taps at all sides of her door, and then enters, gently. If he is strong and large, he should enter one and a half inches; if he is weak and small, he should enter only one inch.